Localization ability with bimodal hearing aids and bilateral cochlear implants

After successful cochlear implantation in one ear, some patients continue to use a hearing aid at the contralateral ear. They report an improved reception of speech, especially in noise, as well as a better perception of music when the hearing aid and cochlear implant are used in this bimodal combination. Some individuals in this bimodal patient group also report the impression of an improved localization ability. Similar experiences are reported by the group of bilateral cochlear implantees. In this study, a survey of 11 bimodally and 4 bilaterally equipped cochlear implant users was carried out to assess localization ability. Individuals in the bimodal implant group were all provided with the same type of hearing aid in the opposite ear, and subjects in the bilateral implant group used cochlear implants of the same manufacturer on each ear. Subjects adjusted the spot of a computer-controlled laser-pointer to the perceived direction of sound incidence in the frontal horizontal plane by rotating a trackball. Two subjects of the bimodal group who had substantial residual hearing showed localization ability in the bimodal configuration, whereas using each single device only the subject with better residual hearing was able to discriminate the side of sound origin. Five other subjects with more pronounced hearing loss displayed an ability for side discrimination through the use of bimodal aids, while four of them were already able to discriminate the side with a single device. Of the bilateral cochlear implant group one subject showed localization accuracy close to that of normal hearing subjects. This subject was also able to discriminate the side of sound origin using the first implanted device alone. The other three bilaterally equipped subjects showed limited localization ability using both devices. Among them one subject demonstrated a side-discrimination ability using only the first implanted device.     

Wet-etch optimization of free-standing terahertz frequency-selective structures

Free-standing frequency-selective surfaces consisting of approximately 10-microm-thick copper films with cross-aperture arrays are found to be tunable toward lower frequencies by means of wet chemical etching. Center frequencies were tuned from 1.57 to 1.53 THz while maintaining high transmittance. Wet etching also adjusts bandwidth, peak transmittance, and sidelobe transmittance. The advantage of the wet-etch technique is demonstrated by employment of these devices as bandpass filters for difluoromethane-based terahertz lasers. Adjustment in aperture dimensions because of etching results in suppression of a competing laser line (133.93 microm) by 15 dB while maintaining high transmittance at the operating wavelength of 192.06 microm.     

MRI observation of heavy metal transport in aquifer matrices down to sub-mg quantities

In this contribution, we report results from MRI studies of the propagation of heavy metal ions through columns packed with sandy aquifer materials. Both sorption of low concentrations of heavy metal ions from water flowing through the column and the formation of sorption traces produced from initially localized higher concentrations of heavy metal ions, and the remobilisation of adsorbed ions with time and changing hydrochemical conditions were studied. Multislice spin-echo and FLASH techniques were used for the imaging experiments. Advantages and problems of the different imaging protocols for the study of aquifer materials are discussed.     

Direct versus conjugate addition to a terphenyl substituted alkynyl difluoro silane

Alkynyl difluoro silanes can react with nucleophiles either directly at the silane unit by displacing the fluorine atoms (direct addition) or, in contrast, the nucleophile can attack the β -carbon of the adjacent alkynyl group (conjugate addition). By using this type of conjugate addition a number of fascinating unsaturated silicon and germanium compounds have been prepared in the past using alkyl substituted phenyl groups as substituents. Therefore we wanted to investigate which regioselectivity isobserved in the case of such an alkynyl difluoro silane shielded by a terphenyl substituent (Mes₂C₆H₃-, Mes =2,4,6-trimethylphenyl). Surprisingly, the reaction with phenyl lithium leads exclusively to direct displacement rather than conjugate addition, which we could prove by X-ray crystallography of 5. Moreover, the synthesis, spectroscopic data and crystal structures of important intermediates to the starting alkynyl difluoro terphenyl silane 2 are presented.     

Direct evidence for the breakdown of the N = 8 shell closure in 12Be

We derive the formalism to obtain spatial distributions of collisional correlation times for macroscopic particles undergoing granular flow from pulsed gradient spin echo nuclear magnetic resonance diffusion data. This is demonstrated with an example of axial motion in the shear flow regime of a 3D granular flow in a horizontal rotating cylinder at one rotation rate.     

Quantitative assessment of rat kidney function by measuring the clearance of the contrast agent Gd(DOTA) using dynamic MRI

Magnetic resonance imaging (MRI) has been applied to assess kidney function in normal rats by monitoring the passage of the extracellular contrast agent GdDOTA. High-resolution images have been obtained using either the rapid acquisition with relaxation enhancement (RARE) or the snapshot pulse sequence. The latter was superior in anatomic definition due to the shorter echo delays used. The GdDOTA induced signal enhancements in the various renal structures were theoretically modeled and the results of the regression analysis then used to estimate local tissue concentrations in renal cortex, inner medulla and outer medulla/pelvis. The concentration-time curves in vena cava and renal cortex were similar and distinctly different from the ones in medulla and pelvis. This is reflected in the time-to-peak (TTP) values, which were TTP (blood) = 0.18 +/- 0.03 < TTP (cortex) = 0.26 +/- 0.05 < TTP (outer medulla) = 0.62 +/- 0.03 < TTP (inner medulla/pelvis) = 0.92 +/- 0.16 min. The initial tracer uptake rates depended linearly on the dose of GdDOTA administered, the value of the uptake rate in the cortex being significantly higher than those in the outer and inner medulla, which were identical within error limits. The initial medullar tracer uptake followed a first-order kinetics. The rate constant k(cl) = (dc[medulla]/dt)/c[cortex] = 3.4 +/- 0.5 min(-1) for the transition from cortex (predominantly blood signal) to medulla (predominantly urine) was considered a measure for the renal clearance. Intravenous administration of furosemide at doses 2.5, 5, and 10 mg/kg led to a dose-dependent decrease of k(cl). This reflects the inhibitory effect of the diuretic furosemide on medullary water resorption and thus the dilution of the GdDOTA in urine.     

Acoustic nonlinearities in adhesive joints

Nondestructive testing of adhesive joints is of great interest. The method of second harmonic generation promises to give early information about failure of adhesive layers. In the case of resonance the amplitude of strain in a soft interface layer is strongly increased and, therefore, the layer considerably contributes to A2, the amplitude of the second harmonic. The nonlinear behavior of such a layer and its influence on A2 was studied by means of the finite element method. In the experimental situation all materials along the sound path contribute to A2. The dependence of the calculated and measured effects on the layer thickness, the velocity of sound, and the nonlinearity coefficient beta are reported.     

Neuronal expression of muskelin in the rodent central nervous system

Background  

The kelch repeat protein muskelin mediates cytoskeletal responses to the extracellular matrix protein thrombospondin 1, (TSP1), that is known to promote synaptogenesis in the central nervous system (CNS). Muskelin displays intracellular localization and affects cytoskeletal organization in adherent cells. Muskelin is expressed in adult brain and has been reported to bind the Cdk5 activator p39, which also facilitates the formation of functional synapses. Since little is known about muskelin in neuronal tissues, we here analysed the tissue distribution of muskelin in rodent brain and analysed its subcellular localization using cultured neurons from multiple life stages.